The present invention is directed to an absorbent article used as a wound dressing. More particularly this invention is directed to an absorbent article having an absorbent, hydrophilic gel layer having a patterned surface.
Historically, exudate from a wound has been dealt with by absorbing it using a dressing containing some type of absorbent material. Examples include dressings such as those shown in U.S. Pat. No. 2,893,388, U.S. Pat. No. 3,018,881 and U.S. Pat. No. 3,073,304. All of these dressings contain a padded absorbent material attached to an adhesive tape backing. The padded absorbent material is applied to the wound to absorb the wound exudate. A difficulty with this type of dressing is that as the wound heals, the scab typically forms in and as part of the pad. Thus, when the dressing is removed, the scab is removed. The disclosures of U.S. Pat. No. 2,923,298, U.S. Pat. No. 3,285,245 and U.S. Pat. No. 3,870,041 have addressed this problem by providing a porous film between the absorbent material and the wound to reduce the likelihood that a scab formed will become attached to the absorbent material.
U.S. Pat. No. 3,888,247 discloses placing a microporous material over the wound and then applying a perforated urethane film containing a wound dressing made in accordance with U.S. Pat. No. 3,285,245 over the microporous tape applied to the wound. U.S. Pat. No. 1,967,923 contains a cellulose sheet membrane or film which protects the dressing and allows air to circulate over the wound. Other wound dressings comprising films are disclosed in U.S. Pat. Nos. 3,645,835, 4,499,896, 4,598,004, and 5,849,325.
A difficulty with dressings which comprise a thin film applied to the wound involves a pooling of exudate under the film if the wound is producing a large amount of exudate. This can result in loosening or removal of the wound dressing. An attempted solution to this problem is provided in U.S. Pat. No. 1,956,695 which discloses a round plaster which contains a rubber film which expands to allow pus to collect under it. This plaster allows the exudate to remain against the wound. Another attempted solution is provided in U.S. Pat. No. 3,521,631 which discloses an impervious sheet placed over a wound with an absorbent material extending over the impervious sheet and around its edges to allow wound exudate to pass into the absorbent material at the edges of the impervious sheet. This entire structure is covered with a backing sheet which is impervious and occlusive. An alleged improvement of the device disclosed in U.S. Pat. No. 3,521,631 is that disclosed in U.S. Pat. No. 4,181,127. An imperforate film of polyurethane contacts the wound which has an absorbent material over it that overlaps the film edges so that the exudate is passed to the absorbent material at the edges of the film. Adhesive tape can be applied over the top of the combination as long as the moisture vapor transmission of the total construction is at least 0.06 mg/cm2 /hour.
More recently the use of so-called xe2x80x9cocclusivexe2x80x9d dressings for pressure sores and ulcers have gained increasing acceptance. A number of wound dressings of this kind are available commercially. Most of these products are formed from several layers, including at least an inner skin-contacting layer and an outer backing layer. The dressing is applied as a cover for the sore or ulcer in a size providing a margin around the wound area that adhesively seals to the skin. The inner layer contains water-absorptive materials, so that fluid from the wound is absorbed into the layer, making it possible to keep the dressing in place for at least several days. Such occlusive dressings tend to promote healing by maintaining the wound under moist conditions, and serve as a barrier against bacterial infection.
While previously known occlusive dressings have overcome some of the problems associated with the management of wounds, they have been found to have certain limitations or disadvantages that have not heretofore been overcome. Absorption of fluid by the portion of the absorptive layer in contact with the wound causes the central portion of the applied dressing to swell and push against the wound. Continued swelling can induce separation of the adhesive layer from the skin outside of the wound area. Fluid may enter between the inner surface absorptive layer and the surrounding skin, working its way outward until it reaches the periphery of the dressing. A primary concern is that such leakage provides a tract for the invasion of pathogenic microorganisms. Also, such leakage can cause skin maceration, leading to enlargement of the wounds.
Leakage of the wound exudate is objectionable because of its unpleasant odor soils bedding and clothing leading to increased costs because of dressing changes. Further, the dressing must be replaced when leakage develops. The more absorptive material included in the absorptive layer, the greater its fluid-absorbing capacity, but too much absorbency can limit the life of the dressing because of the swelling-induced leakage.
In the management of pressure sores, it is desirable that the occlusive dressing be removable in one piece. This minimizes the need to cleanse the wound between dressing applications. At the same time, stripping of the central portion of the dressing from the wound can damage healing tissue.
In an effort to ameliorate some of the foregoing difficulties, a wound care product in current use utilizes a hydrocolloid absorbent that partially loses its integrity after absorbing wound fluid. The portion of the absorbent in contact with the wound is converted to a gel-like material. When the dressing is removed, a portion of this gel material is left in the wound, and must be removed to permit examination and/or before applying another dressing. A wound dressing of the decomposing gel-forming type is disclosed in U.S. Pat. No. 4,538,603. This dressing utilizes a three-layer composite, also generally described in U.S. Pat. No. 3,972,328. A layer of semi-open cell foam material is interposed between the hydrocolloid-containing adhesive layer and an outer film layer. The hydrocolloid material may disintegrate within the adhesive layer, into a non-structural gel on absorbing wound fluid.
An alternative approach is to use a porous, non-adherent skin-contacting layer in an attempt to separate the hydrophilic absorbent material from the wound. However, as the absorbent layer expands on contact with wound exudate, the absorbent tends to swell and protrude or xe2x80x9cmushroomxe2x80x9d, i.e. expand and extend through the pores of the barrier film and contact the wound surface. As with the previous hydrocolloid dressings, effective cleansing is required to wash out the absorbent material from the wound, which must be carried out carefully and gently to avoid damage to the wound bed and newly formed tissue.
This invention provides an absorbent dressing comprising a hydrophilic gel absorbent layer having a patterned surface on at least one major surface thereof. The patterned surface allows greater surface area for absorption of wound exudate when oriented toward the wound surface, while reducing the absorbent surface area in direct or indirect contact with the wound. More significantly, the patterned surface reduces the propensity of the absorbent layer to swell and push against the wound, avoids mushrooming (i.e. expansion of the gel layer through a porous film) and further avoids premature separation of the adhesive layer from the skin. By providing the gel absorbent layer with a patterned surface, the gel may swell into the voids of the patterned surface. Further, the patterned absorbent layer tends to maintain its integrity when hydrated and has a reduced propensity to disintegrate into smaller particles.
The present invention also provides a wound dressing comprising a fluid permeable facing layer and moisture vapor permeable backing layer with the absorbent layer disposed between the two. Preferably the backing layer is both moisture vapor permeable and liquid impermeable. The wound dressing may further comprise a layer of pressure sensitive adhesive to secure the dressing to the skin.
The wound dressing of the present invention advantageously can remove excess exudate from the wound, maintain a moist wound environment, allows gas exchange so that oxygen, water vapor and carbon dioxide can pass through the dressing, is thermally insulating to maintain the wound at body temperature, may be impermeable to liquids and microorganisms to minimize contamination and infection, may be non-adherent to the wound so that no damage is done to the granulating tissue, and minimizes the need to cleanse the wound of dressing material. Further the wound dressing of the present invention can be essentially transparent to allow visual inspection of the wound without removal of the wound dressing.